This invention relates to a worm drive gearbox assembly having a variable speed output shaft.
Typically, worm drive gearbox assemblies are used in industrial machines to step down the shaft speed of the output from a drive motor. The drive motor typically is attached to rotate an input shaft of the gearbox assembly. The input shaft drives an output shaft through a series of gears including a worm gear such that the output shaft rotates at a reduced speed relative to the speed of the input shaft. Often the reduced speed of the output shaft is all that is required to properly accommodate all machine operations. However, in some instances a further gearbox having selectable gearing is attached driven by the output shaft of the worm drive gearbox to provide a variable output required to accommodate desired machine operation at an additional cost.
For this reason there is a need for a worm drive gearbox that can both step down input shaft speed and provide a variable output shaft speed.
The invention is a worm drive gearbox assembly including multiple drive gears that are selectively engageable to vary the speed of an output shaft.
The gearbox assembly includes an input shaft that is rotated at a first speed by an external power source. The input shaft includes a gear head to drive a first intermediate shaft. The first intermediate shaft includes multiple drive gears. The drive gears correspond to multiple driven gears disposed on a second intermediate shaft. The multiple driven gears are movable axially along the second intermediate shaft by shift levers to selectively engage or disengage specific gear combinations.
In another embodiment of the subject gearbox assembly an input shaft supported by the housing drives first and second intermediate shafts at a common speed. A third intermediate shaft includes two clutch assemblies disposed at opposite ends. The third shaft is transverse to the first and second intermediate shafts. Each of the clutch assemblies includes a driven gear that engages with a drive gear of one of the first and second intermediate shafts. The first intermediate shaft includes a worm gear that engages a worm gear on the third shaft when the corresponding clutch is actuated. The third shaft is driven by actuating one of the clutches to engage one of the first and second intermediate shafts. The speed of the third intermediate shaft depends on which of the intermediate shafts is engaged. The third intermediate shaft includes a final drive gear to drive a final driven gear disposed on the output shaft.
The gearbox assembly of the subject invention provides a worm drive gearbox assembly that provides the shaft speed step down function while providing for selection of various output shaft speeds.